Before the world was protected by towering black steel walls, humanity lived in fear of the monsters beyond them. Now, centuries later, the kingdom of Elysium believes itself safe under the divine protection of the Dragon God, Zenith.

Assigned to Frostbourne Citadel, the kingdom's most remote outpost and refuge for the elderly, a young Golden Guard expects nothing more than an uneventful life of endless winter and lonely nights. The strange stories told by the aging residents of unseen visitors, impossible sounds, and divine visions seem like little more than fading memories.

But when a mysterious knocking begins beneath the citadel, his search for its source uncovers signs that something impossible has been hidden beneath Elysium's holiest sanctuary, forcing him to question everything he thought he knew about his kingdom.

In a world where monsters are meant to exist only beyond the walls, the greatest threat may have been hidden within them all along.